The present invention generally relates to medical devices, more particularly to a diagnostic urethral assembly and attendant methodology for assessing lower urinary tract symptoms.
A diagram of the male urinary bladder and urinary passage (i.e., the lower urinary tract) is presented in FIG. 1. The bladder 200 temporarily stores urine 210 and periodically expels it when the bladder neck 220 opens, as the bladder 200 contracts. Urine 210 passes through the prostatic urethra 230, which is completely surrounded by the prostate 240. The distal limit of prostate 240 is marked by a small projection called the verumontanum 250. This is a important landmark because distal thereto, is the external urethral sphincter 260, which relaxes prior to the urination process beginning. Beyond this is the urethra 270, affording a free passage of urine 220 external to body, beyond the external urethral meatus 280.
Presently, millions of men in the United States alone exhibit some form of lower urinary tract symptoms (LUTS), with bladder outlet obstructions (BOOs) being a major subgroup of LUTS. BOOs are primarily caused by the enlargement of the prostate gland (e.g., benign prostate hyperplasia (BHP)) which results in radial compression of the urethra surrounded thereby (i.e., the prostatic urethra), thus obstructing (i.e., constricting) urine flow, resulting in incomplete emptying of the bladder (i.e., there being what is clinically referred to as a xe2x80x9cpost void residualxe2x80x9d (PVR) remaining in the bladder). Persons exhibiting an abnormal PVR will often need to urinate more frequently, and are likely to experience other physical discomfort, such as frequent urges to urinate, and physical exhaustion due to sleep deprivation, a condition clinically referred to as nocturia. Heretofore, such symptoms would be treated using surgical procedures such as transurethral resection of the prostate (TURP), or non-surgical procedures such as thermal treatment of the prostate.
As bladder outlet obstruction patients are a subgroup of patients with LUTS, proper treatment of the specific problem requires a knowledge of complete urodynamic status of the patient in order determine the cause of the symptoms. Causes may include bladder deficiencies such as bladder decompensation or hypertrophy, sphincter dysnergia, prostatic obstruction, urethral lesions and others.
There are diagnostic procedures available to clinical urologists, the purpose of which is to assess the physiologic properties of the lower urinary tract and symptoms related thereto. Such tests, which address the filling/emptying conditions (i.e., dynamics) of the bladder, include, but are not limited to, the use of video fluoroscopy simultaneously with the holding and release of urine, cystometry, urethral pressure profiling, ultrasonic volume assessments, and uroflowmetry. The subject invention provides additional heretofore unknown diagnostic options which allow for relatively simple and increased understanding of the urinary tract by assessing the elements (i.e., structures or architecture) thereof, more particularly the prostatic urethra and their influence on urine flows.
One of the urodynamic tests frequently performed in urodynamic investigations is cystometry, a test of bladder function in which pressure and volume of fluid in the bladder is measured during filling, storage, and voiding. A cystometry study is performed to diagnose problems with urination, including incontinence, urinary retention, and recurrent urinary tract infections. Urinary difficulties may occur because of weak or hyperactive sphincter or detrusor (i.e., the main muscle of the bladder wall), or incoordination of their two activities. Infection of the bladder or urethra may cause incontinence, as can obstruction of the urethra from scar tissue, prostate enlargement, or other benign or cancerous growths. Loss of sensation due to nerve damage can lead to chronic overfilling.
This test of detrusor muscle function generally consists of distending the bladder with a known volume of a fluid (i.e., liquid (e.g., water, saline, etc.) or gas (e.g., air, carbon dioxide, etc.)) while recording the intravesical pressure. The desired fluid may be introduced either through the urethra or suprapubically, in most cases the fluid is instilled through a double lumen catheter at a rate of approximately 10 cc/min, with the catheter employed permitting both filling of the bladder and recording of bladder pressure. As the bladder is composed mostly of small muscles, which are to a large degree under voluntary control, and muscle bundles which run in different directions and from layer to layer, adaptation of the bladder to changing fluid volume is primarily due to the viscal-elastic property of the organ. The bladder wall, in a healthy individual, is able to expand without any significant increase in tension as the bladder fills with fluid.
When the bladder is artificially filled, the pressure which is required to fill that bladder will provide for clinical characterization of the bladder and its general health. If a bladder is non-compliant, the pressure to fill the bladder will increase prematurely. If it is decompensated, meaning it has lost some of its tone, the filling pressure will be minimal while the bladder volume may be large. When the bladder is becoming full, the patient will experience a strong sensation of needing to urinate.
In a typical cystometric study, the filling phase looks at the bladder""s ability to comply to increased volume. The detrusor muscle normally expands as volume increases so that the bladder initially rises very little in pressure to the time the patient voids (i.e., in a plot of pressure against volume of contents during filling (i.e., a xe2x80x9ccystometrogramxe2x80x9d (CMG)), the early portion of this graph is substantially flat for a healthy individual). The normal bladder should not begin contractions during filling and should initially expand without resistance. A feeling of fullness occurs with a volume of about 100-200 ml, with an adult bladder capacity on the order of about 300-500 ml. The sphincter should relax and open when the patient wills it, accompanied by detrusor contractions. During voiding, detrusor contraction should be smooth and lead to a steady urine stream.
If bladder pressure continually rises during filling, it can be due to a number of factors which would bear further investigation. For instance, inability of the bladder to relax during filling, or low bladder volume, may indicate interstitial cystitis, prostate enlargement, or bladder cancer. Contraction of the bladder during filling (i.e., any rise in bladder pressure that is not accompanied by a rise in abdominal pressure) may be due to irritation from infection or cysts, obstruction of the bladder outlet, or neurological disease such as stroke, multiple sclerosis, or spinal cord injury. Diminished sensation may occur with nerve lesions, peripheral neuropathy, or chronic overfilling.
A procedure generically referred to as xe2x80x9cbedside cystometryxe2x80x9d is used to determine, at a basic level, whether the bladder appears decompensated. This is accomplished by simply filling the bladder through a catheter with a known fluid volume, often ranging from about 250-400 ml. The patient is ask to inform the physician when he or she has a strong urge to urinate. Should the patient lack such urge, even when the bladder accommodates the introduced fluid volume, it is likely that some degree of bladder decompensation is present. As the bladder capacities increase, the probability of decompensation increases.
Whether monitoring filling pressures and volumes for the purpose of bladder characterization, or at a bedside procedure which only monitors initiation of flows, information with regard to bladder emptying is typically not acquired. Even if such information were acquired, meaningful diagnosis of BOOs is not possible.
Another standard urodynamic test is called the urethral pressure profile (UPP), (i.e., perfusion urethral profilometry), a procedure which assesses urethral integrity by determining the inward pressure of the urethra continuously along its length (i.e., a measure of the urethra""s response to distention). This test is especially pertinent with respect to patients with incontinence or obstructive symptomatology. Usually a profile of urethral pressure may be obtained by the withdrawal of a pressure recording catheter from the bladder through the urethra. Several methods of profilometry exist including measurement of pressure inside of a balloon which traverses the urethra and also the measurement of the urethral pressure that is transmitted against a fluid or gas that is infused through a small catheter traversing the urethra.
The UPP is typically carried out by inserting a catheter having a side opening and a lumen communicating with that opening. A dilute saline solution is pumped into the lumen and out through the side opening at a fixed rate, while the catheter is steadily withdrawn from the urethra at a substantially constant speed. A plot of the back pressure in the line between the pump and the side opening, against the physical distance of the opening along the urethra, yields the UPP. Typically, as the opening passes a location of constriction, whether normal or abnormal, the back pressure rises, and appears as a spike or hump in the graphical representation of pressure as a function of distance. A further parameter derived from UPP testing is what is called the maximum urethral closure pressure, which is the difference between the maximum pressure derived by the UPP test and the intravesical pressure of the bladder.
What are known in the art as membrane catheters are closed systems also used in obtaining UPPs. Here, the liquid that enters the catheter under pressure serves to expand a thin balloon or elastic element which is located adjacent the end of the catheter. The fluid is captive in the balloon and cannot flow out of the catheter. Single or double membrane catheters are frequently used for recording such urethral pressure profiles. As they are manually or mechanically withdrawn from the bladder cavity, the balloons will traverse the entire length of the urethra and serve to transmit pressure through the liquid with which they are inflated back to a chart recorder or other type of recording device.
A high pressure point in a UPP may be due to poor compliance or obstruction. As UPP procedures rely on very sensitive and indirect measurement, which is not always repeatable, perfusion profilometry is often replaced by the use of catheter micro-tip transducers that record pressure directly. Despite methodology, the diagnostic value of static UPP is limited because it is a study that is performed neither during filling and/or storage, nor during emptying. Static infusion profilometry does have value in evaluating artificial sphincter function, or a potential site of obstruction.
In the paper of Schafer et al. xe2x80x9cObstructed and Unobstructed Prostatic Obstruction: A Plea for Urodynamic Objectivation of Bladder Outflow Obstruction in Benign Prostatic Hyperplasia, Urology, [month] 1989, Vol. _, No. 6, pp. 198-203, the following assessment is noted in the summary: xe2x80x9cThe pathophysiological concept for transurethral resection of the prostate for the treatment of symptomatic benign prostatic hypertrophy centers around xe2x80x9cprostatic obstruction.xe2x80x9d This blind study using advanced computer-assisted analysis of urodynamic pressure/flow studies confirms previous reports to the effect that a significant number ( greater than 25%) of patients undergoing prostatectomy objectively have no obstruction.xe2x80x9d Schaefer et. al conducted a trial on 39 patients who later went on to have a TURP. During the trial advanced level pressure flow studies were conducted on all the patients suspected to have prostatic obstructions. These patients were divided into three groups with all receiving a TURP. The urodynamic outcomes were then measured following recovery. The table below illustrates the urodynamic improvements according to the minimal urethral opening pressure (pmuo). These patients were arbitrarily referred to as xe2x80x9cunobstructed,xe2x80x9d xe2x80x9cobstructed,xe2x80x9d or xe2x80x9cseverely obstructedxe2x80x9d according to the measured pmuo.
Urologists specializing in this field would recognize that only the severely obstructed patients had good urodynamic improvement and significant reduction in the PVR. The xe2x80x9cobstructedxe2x80x9d patients experienced slight improvement in urine flow rates, however, this improvement was arguably so minimal that the TURP procedure may not have been considered sufficiently beneficial to justify the discomfort and attendant risks of the procedure. The result of this study illustrate that in 20 of the 39 patients who received the TURP benefitted greatly. These patients were those with minimal urethral opening pressures of  greater than 40 cm H2O.
Due to the fact that BOO patients are only a subgroup of patients with LUTS, proper treatment of the specific problem requires complete knowledge of the urodynamic status of the patient in order determine whether the patient""s symptoms are caused by BOO, or from bladder deficiencies (e.g., bladder decompensation), or sphincter dysnergia. While comprehensive knowledge of the bladder-urethra interaction during urination may be obtained using complex urodynamic procedures, and UPP, most urologists are currently reluctant to perform such procedures prior to invasive, or minimally invasive, procedures directed to debulking the prostatic urethra. Furthermore, from the aforementioned discussion of cystometry, UPP, and pmuo, it may be appreciated that assessing the likelihood of improvement of the patients urine flow parameters following a dis-obstruction therapy such as TURP is possible, it is not however straight forward, without risk, and subject to a great deal of uncertainty.
It is the objective of the assembly and attendant methodology of the subject invention to provide the urologist additional clinical diagnostic information. The diagnostic assembly of the subject invention provides core information which are at least in part being sought by both the cystometry and UPP, however, unlike either of these procedures, the subject invention provides for dynamic fluid assessment, and further provides for the profiling of the urethra at a specific contact pressure, and simultaneously permits assessment of the effect of pressure on the entire prostatic urethra which may optionally include the external sphincter region.
The subject invention, whether it be the assembly, or the attendant methodology, provides for the easy acquisition of reliable diagnostic information by allowing the patient""s true urination patterns to be observed and the physiological workings of the prostatic urethra ascertained in association therewith.
A diagnostic urethral assembly, preferably in the form of a kit, is generally provided. The assembly includes an elongate body having a fluid passageway and an elongate support member selectively positionable within the fluid passageway of the elongate body. The elongate body has a radially responsive wall segment, the elongate body being positionable within a lower urinary tract such that the radially responsive wall segment is adjacent a prostatic urethra. The elongate body is adapted to be in fluid communication with a bladder. The assembly has a first operably selective condition wherein the elongate support member is translatable relative to the elongate body so as to permit sequential and incremental radial compression of the radially responsive wall segment by the prostatic urethra in furtherance of defining architecture associated with the prostatic urethra. The assembly further has a second operably selective condition wherein fluid distally introduced into the elongate body radially expands the radially responsive wall segment into conforming engagement with the prostatic urethra in furtherance of obtaining a mold of same.
The subject invention seeks to provide the urologist with first, the ability to assess the flow of urine in an actual urination cycle to determine the contribution of flow rate/pressure irregularities on bladder outlet, prostatic urethra, and external sphincter. This is accomplished by the selective movement of an elongate support member within a body of the assembly which will receive the flowing urine at any point along these regions of the urethra while allowing the natural anatomic restrictions to effect the flow by providing a collapsible region in the catheter which is easily responsible to any restrictive regions.
The subject invention further seeks to provide for the assessment of the compressive regions of the urethra by forming a mold, casting or impression of the interior of the urethra at specific pressure conditions. Similar to a UPP, the measurement provides useful information about the compliance of the urethra along its length, however, in contradistinction to a UPP, it provides the ability to ascertain the opening pressure of the urethra while simultaneously identifying the exact location of the obstruction which is effecting the flow.
The foregoing and other objects, features, and advantages of the invention will be apparent with reference to the figures, the DETAILED DESCRIPTION OF THE INVENTION, and the claims hereinafter. The figures are not necessarily to dimensional or geometric scale, nor do they necessarily represent structures in accurate or representative relative scale. Emphasis rather is placed upon illustrating principals of the invention in a clear manner.